IMBE Block Multiplexing for LTE PTT Bandwidth Utilization
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Solution Overview
Problem
Current public safety wireless networks face inefficiencies in bandwidth usage during push-to-talk (PTT) services over LTE, particularly due to the variable length of ISSI packets and the need to allocate resources for the largest possible packet size, leading to unused bandwidth when using persistent or semi-persistent scheduling.
Innovation Solution
The method involves utilizing spare bandwidth by appending enhanced data to IMBE frames within basic IMBE blocks or sending it as a manufacturer-specific block, allowing for the transmission of supplemental information without requiring the user to win the floor, and setting up a dedicated EPS bearer for prolonged sessions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If persistent or semi-persistent scheduling is used for ISSI packets, then resource allocation is simplified and signaling overhead is reduced, but bandwidth utilization deteriorates due to unused bandwidth when packets are smaller than allocated size
Solution Approach 1:
The patent merges ISSI packets with IMBE voice blocks into a single transmitted unit. When voice traffic is present, the ISSI packet is combined with the IMBE block, allowing the same radio resources to carry both control signaling and voice data simultaneously, thereby eliminating wasted bandwidth while maintaining the simplicity of persistent scheduling.
Solution Approach 2:
The IMBE block serves multiple functions: it carries voice data in its primary role, and simultaneously serves as a carrier for ISSI packets when voice traffic is present. This multi-functionality allows the same allocated resources to be fully utilized regardless of whether voice traffic is present or not, resolving the bandwidth waste problem.
2Productivity
If resources are allocated for the largest possible ISSI packet size, then all packet sizes can be transmitted without fragmentation, but bandwidth is wasted when smaller packets are transmitted
Solution Approach 1:
By combining ISSI packets with IMBE voice blocks, the patent ensures that the full allocated bandwidth is utilized. The IMBE block fills the space that would otherwise be wasted, allowing maximum resource utilization while maintaining the ability to transmit packets of various sizes without fragmentation.
Solution Approach 2:
The patent changes the parameter of packet structure by embedding ISSI packets within IMBE blocks. This structural transformation allows the transmission medium to carry additional information (ISSI packets) within the existing voice transmission framework, effectively increasing the information density without requiring additional bandwidth allocation.
3Reliability
If additional information is transmitted separately from voice packets, then data can be sent reliably, but resource allocation increases and bandwidth efficiency decreases
Solution Approach 1:
The patent merges ISSI packets (carrying control signaling and additional information) with IMBE voice blocks into a single transmission unit. This merging ensures reliable delivery of both voice and data through the same robust voice channel while eliminating the need for separate resource allocation, thereby maintaining reliability without increasing resource usage.
Solution Approach 2:
The IMBE block is transformed into a universal carrier that simultaneously transports voice data and ISSI packets. This multi-functional approach ensures that the same reliable voice transmission mechanism serves dual purposes, eliminating the need for separate dedicated channels for data transmission.
Data Source
AI summary
For voice traffic over-the-air in LTE, persistent schedule (PS) or semi-persistent (SPS) scheduling would be the preferred method as they minimize signaling messages. In PS or SPS, resources are pre-allocated to the UE 402 at regular intervals (e.g., every 20 milliseconds). At each time slot, the UE will generally transmit an IMBE frames which are encoded in ISSI packet. In ISSI, other data streams are multiplexed with the IMBE frame and thus the packet size varies depending on its position within a super-frame. For PS or SPS, eNodeB must allocated sufficient resources to support the largest packet that. Therefore, there is spare capacity when the packet is not of the largest size. The exemplary embodiments specify ways to use spare capacity to transfer data.